# 7 Bung - Rubber Stopper - with Airlock Hole

When it comes to fermentation, the key is to keep the oxygen away. This rubber stopper may look pretty simple, but it plays a very big role within the process. Constructed from a solid rubber material, this stopper features a perfectly sized hole to fit an airlock. Simply insert this stopper into the mouth of your fermenter or carboy, add the airlock, and you have an oxygen free zone.

#7 Dimensions: 1 17/16” Bottom Diameter; 1 3/16” Top Diameter